Novel C1 symmetric zirconocenes containing substituted fluorenyl moieties for the polymerization of olefins

Abstract The synthesis and polymerization behavior of four new asymmetric ansa -metallocenes containing a 2,7-disubstituted fluorenyl moiety and an indenyl moiety is reported. Three of the four catalysts, dichloro[η 5 -1-indenyl(1-methylethylidene)-[2,7-bis-(2,4,6-trimethylphenyl)-η 5 -9-fluorenyl]zirconium ( 11 ), dichloro[η 5 -1-indenyl(1-methylethylidene)-[2,7-bis-(2,6-dimethylphenyl)-η 5 -9-fluorenyl]zirconium ( 12 ), and dichloro[η 5 -1-indenyl(1-methylethylidene)-[2,7-bis-(2-methylphenyl)-η 5 -9-fluorenyl] zirconium ( 13 ) were highly active for the polymerization of both ethylene and propylene when activated with excess methylaluminoxane (MAO). Dichloro[η 5 -1-indenyl(1-methylethylidene)-[2,7-dibenzyl-η 5 -9-fluorenyl]zirconium ( 14 ) was poorly active for the polymerization of ethylene and was therefore not evaluated as a propylene catalyst. The activities for propylene polymerizations with catalysts 11 – 13 increased as the size of the substituents around the ligand framework increased, following the trend 11 > 12 > 13 . Molecular weights of the polypropylenes decreased as the temperature was increased. The molecular weight data follows the same trend ( 11 > 12 > 13 ) as the activity data, wherein the largest substituents gave rise to the highest molecular weights.